Laminated glass is less likely to scatter even when shattered by external impact and can be safely used. Due to this advantage, laminated glass has been widely used, for example, in front, side, and rear windshields of vehicles including automobiles and windowpanes of aircraft, buildings, or the like. A known example of laminated glass is a type of laminated glass including at least a pair of glass plates integrated through, for example, an interlayer film for laminated glass which contains a liquid plasticizer and a polyvinyl acetal resin.
A recent growing need is the development of a head-up display (HUD) which presents meters showing vehicle driving data (e.g. driving speed information) within a usual range of vision in the front windshield of a vehicle.
Various types of HUDs are known. The most typical one is a HUD designed such that a display unit of an instrumental panel projects information (e.g. driving speed information) sent from a control unit onto a front windshield to enable a driver to view the information at a usual viewpoint, namely, within a usual range of vision in the front windshield.
An example of interlayer films for laminated glass for a HUD is an interlayer film for laminated glass having a wedge shape with a predetermined wedge angle proposed in Patent Literature 1. This interlayer film can solve a HUD's drawback that a meter image displayed on a laminated glass appears double.
Patent Literature 1 also discloses a laminated glass which is partially free from the HUD's drawback of double meter image phenomenon. Yet, not the entire face of the laminated glass is free from the double meter image problem.
The applicant of this application discloses in Patent Literature 2 an interlayer film for laminated glass, including a light-emitting layer that contains a binder resin and at least one light-emitting material selected from the group consisting of a light-emitting powder, a luminescent pigment, and a luminescent dye. The light-emitting material such as a light-emitting powder, a luminescent pigment, a luminescent dye, or the like emits light when it is irradiated with light having specific wavelengths. When an interlayer film for laminated glass including such a light-emitting material is irradiated with light, light-emitting particles contained in the interlayer film emit light, thereby displaying high contrast images.